No.
The following is not valid HTML at all.
<font color = "black" i class="material-icons md-48">check_circle_outline</i>
Some browsers may read that and try to guess what you meant, but it would be better to get the syntax right at the start. For example, leaving off the closing font tag may work, but you are leaving it up to the browser guess.
It is never valid to leave off the brackets as you have done between the font and i tags.
The following is the valid HTML version of the above.
<font color="black"><i class="material-icons md-48">check_circle_outline</i></font>
